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J. E. Colwell, L. W. Esposito, M. Sremcevic (LASP, University of Colorado)
The Cassini UVIS High Speed Photometer (HSP) measures the intensity of starlight occulted by the rings of Saturn at wavelengths between 110 and 190 nm and at a sampling rate of up to 500 times per second. The HSP has observed seven occultations of portions of Saturn's ring system at a variety of viewing geometries. Taken together with the Voyager PPS observation of the occultation of the star Delta Sco, these observations show a significant variation in the opacity of the A ring as a function of viewing geometry and position in the ring. The differences in opacity persist in regions strongly perturbed by density waves showing that the effect is occurring at a smaller length scale than the typical density wave wavelength of ~1-10 km. This variation can be understood in terms of gravitational wakes which are aligned, gravitationally bound, highly elongated and sheared structures in the ring. In some viewing geometries star light is able to pass between these aligned wakes while in others the wakes block the gaps between them leading to higher effective optical depths. We will describe the initial set of star occultations observed by UVIS and their implications for the structure, orientation, spacing, and spatial distribution of gravitational wakes in Saturn's rings. This research was supported by NASA.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.